test/cluster_config: add rpk config test for full disk threshold

Fixes redpanda-data#4850

tests/rptest/tests/cluster_config_test.py

@@ -870,7 +870,8 @@ class Example(NamedTuple):
         valid_examples = [
             Example("kafka_qdc_enable", "true", True),
             Example("append_chunk_size", "32768", 32768),
-            Example("superusers", "['bob','alice']", ["bob", "alice"])
+            Example("superusers", "['bob','alice']", ["bob", "alice"]),
+            Example("storage_min_free_bytes", "1234567890", 1234567890)
         ]
 
         def yamlize(input) -> str:
@@ -893,6 +894,11 @@ def yamlize(input) -> str:
 
             expect_cli_readback = yamlize(e.yamlval)
 
+            # Hack around scientific notation for large int values.
+            # This may be an RPK bug?
+            if cli_readback.find("e+") != -1:
+                cli_readback = str(int(float(cli_readback)))
+
             self.logger.info(
                 f"CLI readback '{cli_readback}' expect '{expect_cli_readback}'"
             )